Light-emitting diode and backplane and led display including the same

ABSTRACT

A light-emitting diode (LED) includes a first semiconductor layer, an active layer, and a second semiconductor layer that are sequentially stacked, and includes a first electrode pad, a second electrode pad and a third electrode pad disposed on the second semiconductor layer in a direction from a corner of the second semiconductor layer to an opposite corner of the second semiconductor layer. An LED includes a first electrode pad disposed at a center of the LED and in contact with a P-type semiconductor layer and a second electrode pad in contact with an N-type semiconductor layer, wherein the second electrode pad is disposed a maximum distance away from the first electrode pad on the same surface.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation of U.S. patent application Ser. No.16/831,194, filed Mar. 26, 2020, in the US Patent and Trademark Office,which application is based on and claims priority under 35 U.S.C. § 119to Korean Patent Application No. 10-2019-0131594, filed on Oct. 22,2019, in the Korean Intellectual Property Office, the disclosure ofwhich is incorporated by reference herein in its entirety.

BACKGROUND 1. Field

The disclosure relates to light-emitting devices and related devices,and more particularly, to light-emitting diodes (LEDs) and backplanesand LED displays including the same.

2. Description of Related Art

Recently, displays have been changing from liquid crystal displays(LCDs) that use liquid crystals to light-emitting diode (LED) displaysthat use LEDs directly as light sources. As an LED is used as a pixellight source, when an LED display is manufactured, a plurality of microLEDs are transferred to a panel substrate. Through this transfer, themicro LEDs are in electrical contact with each pixel.

SUMMARY

Provided are light-emitting diodes (LEDs) that may ensure a sufficientmounting margin (bonding margin) in applying the LEDs to an LED display.

Provided are LEDs having an electrode structure that may be self-alignedin a mounting process.

Provided are backplanes having a structure that allows self-alignment ofthe LEDs.

Provided are LED displays including the LEDs and backplanes.

Additional aspects will be set forth in part in the description whichfollows and, in part, will be apparent from the description, or may belearned by practice of the presented embodiments of the disclosure.

In accordance with an aspect of the disclosure, a light-emitting diodeincludes a first semiconductor layer; an active layer stacked on thefirst semiconductor layer; a second semiconductor layer stacked on theactive layer; and a first electrode pad, a second electrode pad and athird electrode pad disposed on the second semiconductor layer in adirection from a corner of the second semiconductor layer to an oppositecorner of the second semiconductor layer.

The first electrode pad may include a P-type electrode pad, and thesecond electrode pad and the third electrode pad each may include anN-type electrode pad, and the second electrode pad and the thirdelectrode pad may be symmetrically disposed about the P-type electrodepad.

A height of an upper surface of the first electrode pad may besubstantially equal to a height of an upper surface of the secondelectrode pad and a height of an upper surface of the third electrodepad.

One of the first semiconductor layer and the second semiconductor layermay include a P-type semiconductor layer, the other one of the firstsemiconductor layer and the second semiconductor layer may include anN-type semiconductor layer, and the active layer may include a layerfrom which light is emitted.

In accordance with an aspect of the disclosure, a light-emitting diode(LED) includes a first electrode pad disposed at a center of the LED andin contact with a P-type semiconductor layer; and a second electrode padin contact with an N-type semiconductor layer, wherein the firstelectrode pad and the second electrode pad are disposed on a samesurface, and wherein the second electrode pad is disposed a maximumdistance away from the first electrode pad on the same surface.

The light-emitting diode may further include a third electrode pad incontact with the N-type semiconductor layer.

The third electrode pad may be provided on the same surface at aposition symmetrical to the second electrode pad with respect to thefirst electrode pad.

The first electrode pad, the second electrode pad and the thirdelectrode pad may be disposed on a line from a corner of the samesurface to an opposite corner of the same surface.

A height of an upper surface of the first electrode pad may besubstantially equal to a height of an upper surface of the secondelectrode pad and a height of an upper surface of the third electrodepad.

In accordance with an aspect of the disclosure, a light-emittingincludes an N-type semiconductor layer; an active layer stacked on theN-type semiconductor layer; a P-type semiconductor layer stacked on theactive layer; a first trench that penetrates through the P-typesemiconductor layer and the active layer and extends to a portion of theN-type semiconductor layer; a second trench that penetrates through theP-type semiconductor layer and the active layer at a position separatedfrom the first trench and extends to another portion of the N-typesemiconductor layer; an insulating layer covering walls of the firsttrench and the second trench, the insulating layer covering an uppersurface of the P-type semiconductor layer and respective side surfacesof each of the P-type semiconductor layer, the active layer, and theN-type semiconductor layer; a through hole exposing an upper surface ofthe P-type semiconductor layer, the through hole penetrating theinsulating layer formed on the upper surface of the P-type semiconductorlayer between the first trench and the second trench; a first electrodepad that fills the through hole and that is in contact with the P-typesemiconductor layer; a second electrode pad that fills the first trenchand that is in contact with the N-type semiconductor layer; and a thirdelectrode pad that fills the second trench and that is in contact withthe N-type semiconductor layer, wherein the first electrode pad, thesecond electrode pad and the third electrode pad are arranged in adirection from a corner of the light-emitting diode to an oppositecorner of the light-emitting diode.

In accordance with an aspect of the disclosure, a light-emitting diodeincludes an N-type semiconductor layer; an active layer stacked on theN-type semiconductor layer; a P-type semiconductor layer stacked on theactive layer; a trench that penetrates through the P-type semiconductorlayer and the active layer and extends to a portion of the N-typesemiconductor layer; an insulating layer covering each of a wall of thetrench, an upper surface of the P-type semiconductor layer andrespective side surfaces of each of the P-type semiconductor layer, theactive layer, and the N-type semiconductor layer; a first through holepenetrating through a first portion of the insulating layer covering theupper surface of the P-type semiconductor layer, the first through holeprovided on a first side of the trench; a second through holepenetrating through a second portion of the insulating layer coveringthe upper surface of the P-type semiconductor layer, the second throughhole provided on a second side of the trench opposite to the first side;a first electrode pad that fills the trench and that is in contact withthe N-type semiconductor layer; a second electrode pad that fills thefirst through hole and that is in contact with the P-type semiconductorlayer; and a third electrode pad that fills the second through hole andthat is in contact with the P-type semiconductor layer, wherein thefirst electrode pad, the second electrode pad and the third electrodepad are arranged in a direction from a corner of the light-emittingdiode to an opposite corner of the light-emitting diode.

In accordance with an aspect of the disclosure, a light-emitting diodeincludes an N-type semiconductor layer; an active layer stacked on theN-type semiconductor layer; a P-type semiconductor layer stacked on theactive layer; a trench that penetrates through the P-type semiconductorlayer and the active layer and extends to a portion of the N-typesemiconductor layer; an insulating layer covering each of a wall of thetrench, an upper surface of the P-type semiconductor layer andrespective side surfaces of each of the P-type semiconductor layer, theactive layer, and the N-type semiconductor layer; a through holepenetrating through a portion of the insulating layer covering the uppersurface of the P-type semiconductor layer, the through hole provided ona side of the trench; a first electrode pad that fills the trench andthat is in contact with the N-type semiconductor layer; a secondelectrode pad that fills the through hole and that is in contact withthe P-type semiconductor layer, wherein the first electrode pad and thesecond electrode pad are arranged in a direction from a corner of thelight-emitting diode to an opposite corner of the light-emitting diode.

The light-emitting diode may further include a dummy electrode paddisposed at a position symmetrical to one of the first electrode pad andthe second electrode pad with the other one of the first electrode padand the second electrode pad disposed at a center between the dummyelectrode pad and the one of the first electrode pad and the secondelectrode pad, wherein the first electrode pad, the second electrodepad, and the dummy electrode pad are disposed in the direction.

In accordance with an aspect of the disclosure, a backplane includes asubstrate comprising a plurality of pixel regions; and a moldsurrounding each of the plurality of pixel regions, wherein each pixelregion from among the plurality of pixel regions of the substrateincludes a first bonding pad on a center of the pixel region; and asecond bonding pad that is separated from the first bonding pad and thathas a plurality of bonding regions disposed in a direction from a cornerof the pixel region to an opposite corner of the pixel region.

The second bonding pad may be configured to surround the first bondingpad.

Each pixel region from among the plurality of pixel regions may includefour corners, and each bonding region from among the plurality ofbonding regions of the second bonding pad may be positioned at arespective corner of the four corners of the pixel region.

The plurality of bonding regions in the four corners of the pixel regionmay be connected to each other.

Each pixel region from among the plurality of pixel regions maycorrespond to a respective mold region of the mold, and each mold regionof the mold may include a plurality of side walls inclined with respectto a normal direction perpendicular to a surface of the substrate.

The first bonding pad may include an N-type electrode pad or a P-typeelectrode pad.

The second bonding pad may include an N-type electrode pad or a P-typeelectrode pad.

In accordance with an aspect of the disclosure, a backplane includes asubstrate; a mold provided on the substrate to define a plurality ofpixel regions; a first bonding pad provided at a center of each pixelregion from among the plurality of pixel regions; and a second bondingpad separated from the first bonding pad in each pixel region from amongthe plurality of pixel regions, wherein for each pixel region from amongthe plurality of pixel regions, the second bonding pad surrounds thefirst bonding pad, is continuously disposed along a boundary of threeedges of the pixel region, and comprises a plurality of bonding regionsfor bonding a device such that a bonding region from among the pluralityof bonding regions is disposed in each corner of four corners of thepixel region; and wherein each bonding region from among the pluralityof bonding regions in the second bonding pad is wider than other regionsof the second bonding pad and comprises a portion protruding toward thefirst bonding pad.

A light-emitting diode (LED) display may include a substrate comprisinga plurality of pixel regions; a mold surrounding each pixel region fromamong the plurality of pixel regions; and the light-emitting diode inaccordance with an above-noted aspect of the disclosure, mounted in andbonded to a respective pixel region of the substrate to emit light,wherein each pixel region from among the plurality of pixel regions ofthe substrate includes a first bonding pad on a center of the pixelregion; and a second bonding pad that is separated from the firstbonding pad and that has a plurality of bonding regions disposed in adirection from a corner of the pixel region to an opposite corner of thepixel region.

In accordance with an aspect of the disclosure, a light-emitting diode(LED) display includes a substrate including a display driving circuitunit and a plurality of pixel regions electrically connected to thedisplay driving circuit unit; a first bonding pad formed on a center ofeach pixel region from among the plurality of pixel regions; a secondbonding pad formed in each pixel region from among the plurality ofpixel regions, the second bonding pad being separated from the firstbonding pad; an LED that is mounted in each pixel region from among theplurality of pixel regions and that comprises a first electrode pad incontact with the first bonding pad and a second electrode pad in contactwith the second bonding pad; and a mold surrounding each pixel regionfrom among the plurality of pixel regions, wherein for each pixel regionfrom among the plurality of pixel regions, the second bonding padsurrounds the first bonding pad and comprises a plurality of bondingregions, and for each pixel region from among the plurality of pixelregions, the first electrode pad and the second electrode pad aredisposed in a direction from a corner of the pixel region to an oppositecorner of the pixel region.

For each pixel region from among the plurality of pixel regions, the LEDmay further include a third electrode pad that is separated from thesecond electrode pad and that is in contact with the second bonding pad,and the first electrode pad, the second electrode pad and the thirdelectrode pad may be disposed in the direction.

The third electrode pad may include a dummy electrode pad.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other aspects, features, and advantages of certainembodiments of the disclosure will be more apparent from the followingdescription taken in conjunction with the accompanying drawings, inwhich:

FIG. 1 is a schematic plan view of a light-emitting diode (LED) displayincluding a micro LED according to an embodiment;

FIG. 2 is an enlarged plan view of one pixel of FIG. 1 ;

FIG. 3 is a plan view of a micro LED used in an LED display according toan embodiment;

FIG. 4 is a cross-sectional view taken along a direction 4-4′ of FIG. 3and shows a micro LED according to an embodiment;

FIG. 5 is a cross-sectional view taken along the direction 4-4′ of FIG.3 , and shows a micro LED according to an embodiment;

FIG. 6 is a cross-sectional view taken along the direction 4-4′ of FIG.3 , and shows a micro LED according to an embodiment;

FIG. 7 is a cross-sectional view taken along the direction 4-4′ of FIG.3 , and shows a micro LED according to an embodiment;

FIGS. 8 and 9 are plan views of micro LEDs used in an LED displayaccording to an embodiment;

FIG. 10 is a cross-sectional view taken along a direction 10-10′ of FIG.8 , and shows a micro LED according to an embodiment;

FIG. 11 is a cross-sectional view taken along the direction 10-10′ ofFIG. 8 , and shows a micro LED according to an embodiment;

FIG. 12 is a cross-sectional view of a case in which a plurality ofmicro LEDs are transferred to a display substrate through a mold in aprocess of manufacturing an LED display according to an embodiment;

FIG. 13 is an enlarged view of a first region in which one micro LED istransferred in FIG. 12 , and is a plan view of a substrate inside a moldin which the micro LEDs are mounted;

FIG. 14 is a cross-sectional view taken along a line 14-14′ of FIG. 13 ;

FIG. 15 is a cross-sectional view of a case in which micro LEDs arecorrectly aligned and mounted on a substrate;

FIG. 16 is a cross-sectional view of a case in which a micro LED ismounted to the left in FIG. 15 ; and

FIG. 17 is a cross-sectional view of a case in which a micro LED ismounted to the right in FIG. 15 .

DETAILED DESCRIPTION

Reference will now be made in detail to embodiments, examples of whichare illustrated in the accompanying drawings, wherein like referencenumerals refer to like elements throughout. In this regard, embodimentsmay have different forms and should not be construed as being limited tothe descriptions set forth herein. Accordingly, embodiments are merelydescribed below, by referring to the figures, to explain aspects. Asused herein, the term “and/or” includes any and all combinations of oneor more of the associated listed items. Expressions such as “at leastone of,” when preceding a list of elements, modify the entire list ofelements and do not modify the individual elements of the list.

Hereinafter, a light-emitting diode, a backplane, and a light-emittingdiode (LED) display including the same according to an embodiment willbe described in detail with reference to the accompanying drawings. Thelight-emitting diodes described herein may be micro LEDs that may beused to implement micro LED displays (for example, monitors,televisions, etc.). An area of a micro LED may be, for example, 50 μm×50μm or less, but is not limited thereto. In the drawings, thicknesses oflayers or regions may be somewhat exaggerated for clarity of thespecification. The embodiments described below are merely illustrative,and various modifications may be possible from embodiments of thedisclosure. In layer structures described below, when an element orlayer is referred to as being “on” or “above” another element or layer,the element or layer may be directly on another element or layer orthere may be intervening elements or layers.

Referring to FIG. 1 , a light-emitting diode (LED) display 40 accordingto an embodiment includes a substrate 50 and a plurality of pixels 100.The plurality of pixels 100 are mounted on the substrate 50 and areregularly arranged in horizontal and vertical directions. The LEDdisplay 40 may be a micro LED display. One pixel 100 includes first tothird micro LEDs 100A, 1008, and 100C as shown in FIG. 2 . One of thefirst to third micro LEDs 100A, 1008, and 100C may be a micro LEDemitting red light, another one may be a micro LED emitting green light,and the other one may be a micro LED emitting blue light. In this way,since the light emitted from the first to third micro LEDs 100A, 1008,and 100C are different from each other, the material and/or structure ofa material layer in which the light emission occurs in each micro LEDmay be different from each other. However, the stacked structure of allmaterial layers constituting each of the micro LEDs 100A, 1008, and 100Cmay be the same.

All of the first to third micro LEDs 100A, 1008, and 100C may emit thesame color light. For example, the first to third micro LEDs 100A, 1008,and 100C may emit any one of red light, green light, and blue light. Inthis way, when all of the first to third micro LEDs 100A, 1008, and 100Cemit the same color of light (for example, blue light), a member forcolor control or conversion may be placed in front of one or more of thefirst to third micro LEDs 100A, 1008, and 100C, that is, the pluralityof pixels 100. The member may be a color filter, a color converter, or afluorescent material layer. The color filter may be, for example, aquantum dot color filter or may include a quantum dot color filter.

The first to third micro LEDs 100A, 1008, and 100C may be formed bydirectly implanting or transferring separately made micro-LEDs from theoutside to the substrate 50. FIG. 3 is a top view of a micro LED used inthe LED display 100 according to an embodiment. The micro LED of FIG. 3may be any one of the first to third micro LEDs 100A, 1006, and 100C ofFIG. 2 . For convenience of description, the micro LED of FIG. 3 isregarded as the first micro LED 100A, but the structural features to bedescribed may be equally applied to the second and third micro LEDs 100Band 100C.

Referring to FIG. 3 , the first micro LED 100A includes first to thirdelectrode pads 110, 120, and 130 separated from each other. The first tothird electrode pads 110, 120, and 130 are arranged in a diagonaldirection (i.e., in a direction from one corner of the first micro LED100A to an opposite corner of the first micro LED 100A). The firstelectrode pad 110 may be located at the center of an upper surface ofthe first micro LED 100A. The second electrode pad 120 may be located inan upper left corner, that is, inside the upper left corner of the firstmicro LED 100A. The third electrode pad 130 may be located at a lowerright corner, that is, inside the lower right corner of the first microLED 100A. The second electrode pad 120 and the third electrode pad 130may be disposed at other corners, that is, first and second regions A1and A2, respectively. For example, the second electrode pad 120 may bedisposed in the first region A1 and the third electrode pad 130 may bedisposed in the second region A2. Regardless of where the second andthird electrode pads 120 and 130 are located, the second and thirdelectrode pads 120 and 130 may be located at the most distant locationsfrom the first electrode pad 110 on the upper surface of the first microLED 100A. An insulating layer 260 is between the first to thirdelectrode pads 110, 120, and 130. Each of the first to third electrodepads 110, 120, and 130 is surrounded by the insulating layer 260. In anexample, the first electrode pad 110 may be a P-type electrode padcontacting a P-type semiconductor layer of the first micro LED 100A. Inanother example, the first electrode pad 110 may be an N-type electrodepad contacting an N-type semiconductor layer of the first micro LED100A. The second and third electrode pads 120 and 130 may be electrodepads having polarities opposite to those of the first electrode pad 110.For example, when the first electrode pad 110 is a P-type electrode pad,the second and third electrode pads 120 and 130 may be N-type electrodepads. As another example, when the first electrode pad 110 is an N-typeelectrode pad, the second and third electrode pads 120 and 130 may beP-type electrode pads. As still another example, one of the second andthird electrode pads 120 and 130 may be an isolated dummy electrode padwithout being electrically connected to other layers of the first microLED 100A.

FIG. 4 is a cross-sectional view taken along a broken line in adirection 4-4′ of FIG. 3 and shows a first micro LED according to afirst embodiment.

Referring to FIG. 4 , the first micro LED 100A includes a stack 280 andan insulating layer 260 sequentially formed on a substrate 200 and firstto third electrode pads 110, 120, and 130 provided on the insulatinglayer 260 and the stack 280.

In detail, a first material layer 210, a second material layer 220, anda third material layer 230 are sequentially stacked on the substrate200. The first material layer 210 may be or include a firstsemiconductor layer. The first semiconductor layer may include an N-typesemiconductor layer or a P-type semiconductor layer. The N-typesemiconductor layer may include, for example, an N-doped compoundsemiconductor layer. The P-type semiconductor layer may include, forexample, a P-doped compound semiconductor layer. The second materiallayer 220 may be an active layer. The second material layer 220 may be alight-emitting layer that emits light according to combination ofelectrons and holes or may include the light-emitting layer. Forexample, the second material layer 220 may include a multi-quantum well(MQW) layer. The third material layer 230 may be or include a secondsemiconductor layer. The second semiconductor layer may be a P-typesemiconductor layer or an N-type semiconductor layer. One of the firstand second material layers 210 and 230 may be a P-type semiconductorlayer, and the other may be an N-type semiconductor layer. A firsttrench 240 and a second trench 250 are formed in the stack 280 thatincludes the first to third material layers 210, 220, and 230. The firsttrench 240 and the second trench 250 are separated from each other. Asshown in FIG. 4 , the first electrode pad 110 is disposed between thefirst trench 240 and the second trench 250. The first trench 240penetrates through the second and third material layers 220 and 230 andextends to a portion of the first material layer 210. The second trench250 is also formed in the same form as the first trench 240 and mayextend to another portion of the first material layer 210. Side surfacesof the first to third material layers 210, 220, and 230 exposed by thefirst and second trenches 240 and 250 are covered with the insulatinglayer 260. The insulating layer 260 may include an oxide layer or anitride layer, or may include a layer formed of another insulatingmaterial. The insulating layer 260 covers walls of the first and secondtrenches 240 and 250, that is, inner side surfaces of the first andsecond trenches 240 and 250. However, the insulating layer 260 does notfill the first and second trenches 240 and 250. The insulating layer 260extends across a surface of the third material layer 230. A through hole260 h is provided between the first and second trenches 240 and 250. Thethrough hole 260 h penetrates through the insulating layer 260. Thethird material layer 230 is exposed through the through hole 260 h. Theinsulating layer 260 covers an entire upper surface of the thirdmaterial layer 230 around the first and second trenches 240 and 250 andaround the through hole 260 h. The insulating layer 260 may cover bothsides of the stack 280 by extending to both sides thereof. The secondelectrode pad 120 filling the first trench 240 is formed on theinsulating layer 260. The second electrode pad 120 is in contact withthe first material layer 210 exposed by the first trench 240. A surfaceof the first material layer 210 directly contacting the second electrodepad 120 becomes a bottom of the first trench 240. Also, the thirdelectrode pad 130 filling the second trench 250 is formed on theinsulating layer 260. The third electrode pad 130 is in contact with thefirst material layer 210 exposed by the second trench 250. A surface ofthe first material layer 210 directly contacting the third electrode pad130 becomes a bottom of the second trench 250. The first electrode pad110 filling the through hole 260 h is provided on the insulating layer260 between the second and third electrode pads 120 and 130. The firstelectrode pad 110 is in direct contact with the third material layer 230through the through hole 260 h.

The first to third electrode pads 110, 120, and 130 may be formed at thesame time after the contact hole 260 h is formed. The first to thirdelectrode pads 110, 120, and 130 may include the same material. Thefirst electrode pad 110 may include a material different from that ofthe second and third electrode pads 120 and 130. In the latter case, theformation time of the first electrode pad 110 may be different from theformation time of the second and third electrode pads 120 and 130. Uppersurfaces of the first to third electrode pads 110, 120, and 130 may havethe same height as each other. A distance D1 between the first and thesecond electrode pads 110 and 120 and a distance D2 between the firstand the third electrode pads 110 and 130 may be the same or differentfrom each other. The distances D1 and D2 may be determined considering agap between a P-type and N-type bonding electrodes provided on asubstrate (hereinafter, referred to as a bonding substrate) onto whichthe first micro LED 100A is to be mounted or, when the first micro LED100A is bonded to the bonding substrate, gaps between the mold preparedfor self-alignment of the first micro LED 100A and the first micro LED100A.

The substrate 200 may be removed from the first micro LED 100A of FIG. 4. The first micro LED 100A may refer to the remaining part from whichthe substrate 200 is removed. When the first micro LED 100A is bonded tothe bonding substrate through a mold, the first micro LED 100A may bebonded after the substrate 200 is removed.

FIG. 5 is a cross-sectional view taken along a direction 4-4′ of FIG. 3and shows the first micro LED 100A according to a second embodiment.Only parts different from FIG. 4 will be described.

Referring to FIG. 5 , a trench 280 h penetrating through the second andthird material layers 220 and 230 is formed in the stack 280. The trench280 h may be located at the center of the first micro LED 100A or at aposition generally referred to as the center. The trench 280 h extendsto the first material layer 210. Accordingly, the first material layer210 is exposed through the trench 280 h. An exposed portion of the firstmaterial layer 210 is a bottom of the trench 280 h. The geometry of thetrench 280 h may be the same as that of the first trench 120 or thesecond trench 130 of FIG. 4 . The trench 280 h may be formed in the samemanner as the method of forming the first trench 120 or the secondtrench 130 of FIG. 4 . An inner side (wall) of the trench 280 h iscovered with the insulating layer 260, but the bottom thereof is exposed(i.e., not covered with the insulating layer 260). The trench 280 h isfilled with a first electrode pad 430. The first electrode pad 430completely fills the trench 280 h and extends onto the upper surface ofthe insulating layer 260 around the trench 280 h by a given length. Thefirst electrode pad 430 contacts the first material layer 210 throughthe trench 280 h. Since the first electrode pad 430 is in contact withthe first material layer 210 including the N-type semiconductor layer,the first electrode pad 430 may be an N-type electrode pad. Second andthird electrode pads 440 and 450 are positioned on either side of thefirst electrode pad 430 with the first electrode pad 430 as the center.The second and third electrode pads 440 and 450 are in contact with thethird material layer 230 respectively through first and second throughholes 440 h and 450 h respectively passing through first and secondportions of the insulating layer 260. Since the second and thirdelectrode pads 440 and 450 are in contact with the third material layer230 that includes a P-type semiconductor layer, the second and thirdelectrode pads 440 and 450 may be P-type electrode pads. Although thesecond and third electrode pads 440 and 450 extend on the upper surfaceof the insulating layer 260 by a given length, the second and thirdelectrode pads 440 and 450 respectively maintain given distances D1 andD2 from the edge of the first electrode pad 430. The first to thirdelectrode pads 430, 440, and 450 are surrounded by the insulating layer260. The first to third electrode pads 430, 440, and 450 may have thesame height as each other.

FIG. 6 is a cross-sectional view taken along the direction 4-4′ of FIG.3 and shows the first micro LED 100A according to a third embodiment.Only parts different from FIG. 4 will be described.

Referring to FIG. 6 , the first micro LED 100A does not include thethird electrode pad 130 of FIG. 4 and includes a dummy electrode pad 520in the position of the third electrode pad 130. The dummy electrode pad520 is positioned entirely on the insulating layer 260. The dummyelectrode pad 520 does not contact any of the other material layersincluded in the first micro LED 100A. Therefore, the dummy electrode pad520 is completely isolated The dummy electrode pad 520 has the sameheight as the first and third electrode pads 110 and 130. The dummyelectrode pad 520 may be provided for the balance and stability of thefirst micro LED 100A when the first micro LED 100A is mounted on abackplane, which may be referred to as a display panel substrate. Thedummy electrode pad 520 may be, for example, a metal pattern.

The first micro LED 100A illustrated in FIG. 6 may be the same as a casewhen the third electrode pad 130 and the second trench 250 are omittedfrom the first micro LED 100A of FIG. 4 and the dummy electrode pad 520is formed on the insulating layer 260 covering an upper surface of thethird material layer 230. In FIG. 6 , the position of the secondelectrode pad 120 may be interchanged with the position of the dummyelectrode pad 520. In other words, the dummy electrode pad 520 may bedisposed on a left side of the first electrode pad 110, and the secondelectrode pad 120 may be disposed on a right side of the first electrodepad 110.

FIG. 7 is a cross-sectional view taken along the direction 4-4′ of FIG.3 and shows a first micro LED 100A according to a fourth embodiment.Only parts different from FIG. 4 will be described.

Comparing FIG. 5 to FIG. 7 , the first micro LED 100A illustrated inFIG. 7 may be the same as a case when the third electrode pad 450 andthe through hole 450 h are omitted from the first micro LED 100A of FIG.5 and a dummy electrode pad 620 is formed on the insulating layer 260covering the upper surface of the third material layer 230. In FIG. 7 ,the position of the second electrode pad 440 may be interchanged withthe position of the dummy electrode pad 620. In other words, the dummyelectrode pad 620 may be disposed on a left side of the first electrodepad 430, and the second electrode pad 440 may be disposed on a rightside of the first electrode pad 430.

Referring to FIGS. 6 and 7 , each of the dummy electrode pads 520 and620 may be provided to be symmetrical to one of the first and secondelectrode pads 110 and 120 (or 430 and 440), for example, the firstelectrode pad 110 (or 430), with the other one of the first and secondelectrode pads 110 and 120 (or 430 and 440) positioned at the center.

FIG. 8 is a plan view of the first micro LED 100A according to anotherembodiment. Like reference numerals are used to indicate elements thatare substantially identical to the elements described above

Referring to FIG. 8 , the first micro LED 100A includes first and secondelectrode pads 810 and 820 that are diagonally disposed. The first andsecond electrode pads 810 and 820 are surrounded by the insulating layer260. The first electrode pad 810 may correspond to the first electrodepad 110 of FIG. 3 . The second electrode pad 820 may correspond to thesecond electrode pad 120 of FIG. 3 . As shown in FIG. 9 , the secondelectrode pad 820 may be disposed on an opposite side along a diagonalline. In other words, the second electrode pad 820 may be disposed at aposition corresponding to the third electrode pad 130 of FIG. 3 . Inanother example, the second electrode pad 820 may be disposed in a firstarea A11 or a second area A22 as shown in FIG. 8 . As shown in FIGS. 8and 9 , the distance between the first and second electrode pads 810 and820 is maximized when the second electrode pad 820 is disposed at anyposition in a diagonal direction. In other words, in the first micro LED100A, the first and second electrode pads 810 and 820 may be disposed tohave a maximum possible distance from each other when one of the pads ispositioned at the center.

FIG. 10 is a cross-sectional view taken along a direction 10-10′ of FIG.8 and shows a first micro LED 100A according to an embodiment.

Referring to FIG. 10 , the first micro LED 100A may be the same as acase when the third electrode pad 130 and the second trench 250 areomitted from the first micro LED 100A shown in FIG. 4 .

FIG. 11 is a cross-sectional view taken along the direction 10-10′ ofFIG. 8 and shows a first micro LED 100A according to another embodiment.

Referring to FIG. 11 , the first micro LED 100A may be the same as acase when the third electrode pad 450 and the through hole 450 h areomitted from the first micro LED 100A shown in FIG. 5 . In other words,in the first micro LED 100A of FIG. 11 , the second electrode pad(N-type electrode pad) 820 is disposed at the center, and the firstelectrode pad (P-type electrode pad) 810 is disposed at a corner in adiagonal direction.

FIG. 12 schematically illustrates a case when a plurality of micro LEDs,that is, the first, second, and third micro LEDs 100A, 1006, and 100C,are bonded or mounted to a predetermined position of a substrate 360through a mold 300 in an LED display according to an embodiment. Here,the determined position may be a pixel position. The substrate 360 mayinclude a circuit unit 360A for driving the LED display. The circuitunit 360A may be electrically connected to a pixel region where alight-emitting device is mounted. The mold 300 and the substrate 360 maybe collectively referred to as a backplane.

Referring to FIG. 12 , a plurality of micro LEDs, that is, the first,second, and third micro LEDs 100A, 1006, and 100C, respectively arebonded to a plurality of predetermined positions of the substrate 360.In order to guide the bonding of the plurality of micro LEDs, that is,the first, second, and third micro LEDs 100A, 1006, and 100C, the mold300 is provided on the substrate 360. A surface (for example, an entireupper surface) of the substrate 360 on which the plurality of microLEDs, that is, the first, second, and third micro LEDs 100A, 100B, and100C, are to be bonded may be divided into a plurality of bondingregions 360B by the mold 300. The bonding regions 360B may be pixelregions. Each of the bonding regions 360B may have an area on which onemicro LED may be bonded. Accordingly, one micro LED, that is, the first,second, or third micro LED 100A, 1006, or 100C, may be bonded to each ofthe bonding regions 360B divided by the mold 300. Each of the bondingregions 360B may be one sub-pixel region, and one micro LED bonded toeach bonding region 360B may be a sub-pixel emitting red light, greenlight, or blue light.

The plurality of micro LEDs, that is, the first, second, and third microLEDs 100A, 1006, and 100C, may be supplied on the substrate 360 by a wettransfer method, or may be supplied by a transfer method different fromthe wet transfer method. As an example of the wet transfer method, aliquid fluid including a plurality of micro LEDs, that is, the first,second, and third micro LEDs 100A, 1006, and 100C, may flow or besprayed onto the substrate 360 on which the mold 300 is provided. Themold 300 has a structure for guiding the micro LEDs so that one microLED may be mounted in each of the bonding regions 360B. Accordingly, onemicro LED, that is, the first, second, or third micro LED 100A, 1006, or100C, may be mounted in each bonding region 360B while the liquid fluidflows or is sprayed onto the substrate 360. Reference numeral 12Adenotes a unit bonding region. Only one micro LED is bonded in the unitbonding region. Therefore, the unit bonding region may be one sub-pixelregion.

FIG. 13 is a view from the top of the unit bonding region of thesubstrate 360 on which the mold 300 for self-alignment of the firstmicro LED 100A is provided in a bonding process of the first micro LED100A.

Referring to FIG. 13 , a first bonding pad 310 and a second bonding pad320 are provided in the bonding region 360B inside the mold 300. Thefirst and second bonding pads 310 and 320 may be conductive pads. Thefirst bonding pad 310 may be located at the center of the bonding region360B. The center of the mold 300 may coincide with the center of thesubstrate 360 inside the mold 300. The first bonding pad 310 is aportion to be bonded to the first electrode pads 110, 430, and 810 ofthe first micro LED 100A. A wire 321A connected to a power source isconnected to the first bonding pad 310. The second bonding pad 320 isseparated from the first bonding pad 310. The second bonding pad 320 iselectrically insulated from the first bonding pad 310. The secondbonding pad 320 surrounds the first bonding pad 310 except for a portionwhere the wire 321A of the first bonding pad 310 is disposed. The secondbonding pad 320 is continuously disposed along a boundary of the pixelregion defined by the mold 300, for example, along the boundary of threesurfaces (i.e., edges) of the pixel region. Although described herein asa pixel region for convenience, the pixel region defined by the mold 300shown in FIG. 13 may be practically a sub-pixel region to which onemicro LED is bonded. The second bonding pad 320 may include first tofourth bonding regions 320A, 320B, 320C, and 320D provided at fourcorners of the substrate 360 inside the frame 300. As shown in FIG. 13 ,an area of the first to fourth bonding regions 320A to 320D in thesecond bonding pad 320 may be relatively greater than other areas withinthe second bonding pad 320, for example, areas between the first tofourth bonding regions 320A to 320D. The first to fourth bonding regions320A to 320D are regions in contact with the second and third electrodepads 120 and 130 or 440 and 450 of the first micro LED 100A. The firstto fourth bonding regions 320A, 320B, 320C, and 320D respectively mayhave portions P1 to P4 protruding toward the first bonding pad 310. Whenthe first micro LED 100A has an electrode pad configuration as shown inFIG. 6 or 7 , the first to fourth bonding regions 320A to 320D maycontact one electrode pad 120 or 440 and one dummy electrode pad 520 or620. Also, when the first micro LED 100A has an electrode padconfiguration as shown in FIGS. 8 to 11 , the first to fourth bondingregions 320A to 320D may contact one electrode pad, that is, the firstor second electrode pad 810 or 820, disposed in a corner of the firstmicro LED 100A in a diagonal direction.

In this way, the second bonding pad 320 respectively has bondingregions, that is, the first to fourth bonding regions 320A to 320D, atfour corners with the first bonding pad 310 as the center. It ispossible that the first micro LED 100A is rotated or twisted in anydirection in a process of mounting the first micro LED 100A includingthe electrode pads aligned as shown in FIG. 3 , FIG. 8 , or FIG. 9 onthe mold 300. But as long as the electrode pads, that is, the firstelectrode pad 110, the second electrode pad 120, the third electrode pad130, the first electrode pad 810, or the second electrode pad 820,included in the first micro LED 100A face the substrate 360 inside themold 100, the first electrode pad 110 or 810 of the first micro LED 100Amay contact the first bonding pad 310 inside the mold 300. Further, thesecond electrode pad 120 and/or the third electrode pad 130, or thesecond electrode pad 820 may surely contact one of the first to fourthbonding regions 320A to 320D of the second bonding pad 320. As describedabove, the reason why the first micro LED 100A is self-mounted orself-bonded is because two or more electrode pads, that is, the firstelectrode pad 110, the second electrode pad 120, the third electrode pad130, or the first and second electrode pads 810 and 829, are on the samesurface of the first micro LED 100A in a diagonal direction.

FIG. 14 is a cross-sectional view taken along a line 14-14′ of FIG. 13 ,that is, the unit bonding region 12A in a diagonal direction.

Referring to FIG. 14 , a mold region of the mold 300 to guideself-alignment bonding of the first micro LED 100A is provided on bothedges of the substrate 360. Inner side surfaces (i.e., side walls) ofthe mold 300 are inclined to facilitate receiving of the micro LED. Theinclined surface may be inclined with respect to a normal directionperpendicular to a surface of the substrate 360. A width 14D of the mold300 gradually increases toward the substrate 360. The first bonding pad310 is at the center of the substrate 360 inside the mold 300. The firstbonding region 320A of the second bonding pad 320 is on a left side, andthe fourth bonding region 320D of the second bonding pad 320 is on aright side of the first bonding pad 310.

FIG. 15 is a cross-sectional view of a case in which the first micro LED100A is normally mounted (bonded) on the substrate 360 inside the mold300 of FIG. 14 .

Referring to FIG. 15 , the first electrode pad 110 of the first microLED 100A contacts the first bonding pad 310 inside the mold 300. Thethird electrode pad 130 of the first micro LED 100A contacts the firstbonding region 320A of the second bonding pad 320 inside the mold 300.Also, the second electrode pad 120 of the first micro LED 100A contactsthe fourth bonding region 320D of the second bonding pad 320 inside themold 300.

Reference numeral 420 indicates a body including the stack 280 and theinsulating layer 260 of the first micro LED 100A. In FIG. 15 , one ofthe second and third electrode pads 120 and 130 may be a dummy electrodepad.

FIG. 16 illustrates a case in which the first micro LED 100A is mountedto the left side, and FIG. 17 illustrates a case in which the firstmicro LED 100A is mounted to the right side.

Referring to FIGS. 16 and 17 , as long as the first micro LED 100A isintroduced into the mold 300 while maintaining a normal bondingdirection, although the first micro LED 100A is bonded to the left orthe right unlike in FIG. 15 , the first to third electrode pads 110,120, and 130 of the first micro LED 100A may still contact thecorresponding bonding pads on the substrate 360 inside the mold 300.

In this way, even when the first micro LED 100A is mounted to one side,the first to third electrode pads 110, 120, and 130 may contact thecorresponding bonding pads. Accordingly, a temperature and pressureapplied to the first micro LED 100A in a bonding process, for example, aeutectic bonding process may be uniformly and entirely applied to thefirst micro LED 100A. Accordingly, the first micro LED 100A may bestably balanced in the bonding process. The bonding process may be adirect contact bonding method in which the first to third electrode pads110, 120, and 130 and the bonding pads, that is, the first and secondbonding pads 310 and 320, are in direct contact, or an indirect contactbonding method in which a contact member (for example, solder ball) isused between the first to third electrode pads 110, 120, and 130, andthe bonding pads, that is, the first and second bonding pads 310 and320.

A light-emitting diode according to an embodiment includes one centerelectrode pad and two electrode pads disposed around the centerelectrode pad on the same surface. The center electrode pad may includea P-type electrode pad or an N-type electrode pad. The center electrodepad may have a polarity opposite to polarities of the two electrode padsdisposed around the center. The two electrode pads are symmetricallydistributed with the center electrode pad as the center. The threeelectrode pads are arranged in a diagonal direction on the same surfaceso that a distance between the center electrode pad and the twoelectrode pads on the same surface is maximum. Accordingly, a sufficientmargin may be ensured in a process of mounting (bonding) thelight-emitting diode, and the mounting margin is increased, and thus,the mounting (bonding) is easy compared to the related art, and thefailure rate of mounting may be reduced.

Also, when the size of the light-emitting diode is reduced, a sufficientbonding margin (bonding interval) may be ensured even when the degree ofintegration of the light-emitting diode array is increased.

Also, a temperature and pressure applied to the light-emitting diode ina bonding process, for example, a eutectic bonding process, may beuniformly distributed on the entire light-emitting diode, and thus, thestability of the light-emitting diode may be increased during thebonding process.

It should be understood that embodiments described herein should beconsidered in a descriptive sense only and not for purposes oflimitation. Descriptions of features or aspects within each embodimentshould typically be considered as available for other similar featuresor aspects in other embodiments. While one or more embodiments have beendescribed with reference to the figures, it will be understood by thoseof ordinary skill in the art that various changes in form and detailsmay be made therein without departing from the spirit and scope asdefined by the following claims.

What is claimed is:
 1. A light-emitting diode comprising: a firstsemiconductor layer; an active layer stacked on the first semiconductorlayer; a second semiconductor layer stacked on the active layer; and afirst electrode pad, a second electrode pad and a third electrode paddisposed on the second semiconductor layer in a direction from a cornerof the second semiconductor layer to an opposite corner of the secondsemiconductor layer, wherein one of the second electrode pad and thethird electrode pad comprises a dummy electrode pad, and wherein thedummy electrode pad is spaced apart from the second semiconductor layer.2. The light-emitting diode of claim 1, wherein the first electrode padcomprises a P-type electrode pad, wherein the second electrode pad andthe third electrode pad each comprise an N-type electrode pad, andwherein the second electrode pad and the third electrode pad aresymmetrically disposed about the P-type electrode pad.
 3. Thelight-emitting diode of claim 1, wherein a height of an upper surface ofthe first electrode pad is substantially equal to a height of an uppersurface of the second electrode pad and a height of an upper surface ofthe third electrode pad.
 4. The light-emitting diode of claim 1, whereinone of the first semiconductor layer and the second semiconductor layercomprises a P-type semiconductor layer, the other one of the firstsemiconductor layer and the second semiconductor layer comprises anN-type semiconductor layer, and the active layer comprises a layer fromwhich light is emitted.
 5. The light-emitting diode of claim 1, whereinone of the first and second electrode pads is in contact with the firstsemiconductor layer by penetrating through the second semiconductorlayer and the active layer and the other one of the first and secondelectrode pads is in contact with the second semiconductor layer.
 6. Thelight-emitting diode of claim 5, wherein the one of the first and secondelectrode pads has a portion penetrating through the secondsemiconductor layer and the active layer, and wherein an insulatinglayer is between the portion and the second semiconductor layer and theactive layer.
 7. The light-emitting diode of claim 1, whereinthicknesses of the first to third electrode pads are different from eachother.
 8. The light-emitting diode of claim 1, further comprising aninsulating layer between the dummy electrode pad and the secondsemiconductor layer.
 9. The light-emitting diode of claim 8, wherein theinsulating layer is extended on the second semiconductor layer betweenthe first electrode pad, the second electrode pad, and the thirdelectrode pad.
 10. The light-emitting diode of claim 1, wherein thefirst semiconductor layer, the active layer, and the secondsemiconductor layer are sequentially stacked on a substrate, and whereina distance between the substrate and the first electrode pad isdifferent from a distance between the substrate and the other one of thesecond electrode pad and the third electrode pad.
 11. The light-emittingdiode of claim 1, wherein upper surface areas of the first to thirdelectrode pads are the same or different from each other.
 12. Alight-emitting diode comprising: an N-type semiconductor layer; anactive layer stacked on the N-type semiconductor layer; a P-typesemiconductor layer stacked on the active layer; a trench thatpenetrates through the P-type semiconductor layer and the active layerand extends to a portion of the N-type semiconductor layer; a throughhole configured to expose the P-type semiconductor layer, the throughhole provided on a side of the trench; a first electrode pad that is incontact with the N-type semiconductor layer via the trench; a secondelectrode pad that is in contact with the P-type semiconductor layer viathe through hole, and a dummy electrode pad, wherein the first electrodepad, the second electrode pad, and the dummy electrode pad are arrangedin a direction from a corner of the light-emitting diode to an oppositecorner of the light-emitting diode, and wherein the dummy electrode padis spaced apart from the P-type semiconductor layer.
 13. Thelight-emitting diode of claim 12, wherein the dummy electrode pad isdisposed at a position symmetrical to one of the first electrode pad andthe second electrode pad with the other one of the first electrode padand the second electrode pad disposed at a center between the dummyelectrode pad and the one of the first electrode pad and the secondelectrode pad.
 14. The light-emitting diode of claim 12, wherein uppersurface areas of the first electrode pad, the second electrode pad, andthe dummy electrode pad are the same or different from each other. 15.The light-emitting diode of claim 12, further comprising an insulatinglayer between the dummy electrode pad and the P-type semiconductorlayer.
 16. The light-emitting diode of claim 15, wherein the insulatinglayer is extended on the P-type semiconductor layer between the firstelectrode pad, the second electrode pad, and the dummy electrode pad.17. The light-emitting diode of claim 16, wherein the insulating layeris extended in the trench to prevent the first electrode pad from beingin contact with the P-type semiconductor layer and the active layer. 18.A light-emitting diode (LED) display comprising: a substrate comprisinga plurality of pixel regions; a mold surrounding each pixel region fromamong the plurality of pixel regions; and a light-emitting diode mountedin and bonded to a respective pixel region of the substrate to emitlight, wherein the light-emitting diode comprises: a first semiconductorlayer; an active layer stacked on the first semiconductor layer; asecond semiconductor layer stacked on the active layer; and a firstelectrode pad, a second electrode pad and a third electrode pad disposedon the second semiconductor layer in a direction from a corner of thesecond semiconductor layer to an opposite corner of the secondsemiconductor layer, wherein one of the second electrode pad and thethird electrode pad comprises a dummy electrode pad, wherein the dummyelectrode pad is spaced apart from the second semiconductor layer, andwherein each pixel region from among the plurality of pixel regions ofthe substrate comprises: a first bonding pad on a center of the pixelregion; and a second bonding pad that is separated from the firstbonding pad and that has a plurality of bonding regions disposed in adirection from a corner of the pixel region to an opposite corner of thepixel region.
 19. The LED display of claim 18, wherein an area of thesecond bonding pad is larger than an area of the first bonding pad.